Rotary driven percussive tool



Oct. 14, 1952 H. c. REYNOLDS 2,613,662

ROTARY DRIVEN PERCUSSIVE TOOL Filed March 21, 1950 0 2 3' a 55 45 IO 53 49.2 1 ."1.

59 56 47 ll 44 6O 42 4856 4 so 4o 59 4? 43 0 a9| 25395222 26 4 57 45 GI 46 5O |NVENTQR I6 HAROLD C. REYNOLDS HIS ATTORNEY Patented Oct. 14, 1952 UNITED PATENT OFFICE ;RO.TARY,IDRIVEN PERGUSSIVE TOOL Harold C. "Reynbl'd's, Athens, Pa, assignor to IngersoH-R-and Company, New York, N. Y., a corporation "of New ersey Application Marshal, 1950, Serial No. 1511168 '10 Claims. '1

This invention relates to percussive tools, and more particularly to percussive tools having a rotary drive.

'One objectof the invention is to provide .a percussive tool with a rotary drive mechanism.

Another object of theinvention is to isolate the rotary element of the toolfrom the shock of the percussive impact.

Another object is to provide a simple and compact cushioning mechanism for the tool.

Still another object of the invention is toprovide a construction which will insure .long lifeof the cushioning element.

Other objects willbeinpart obvious and in part pointed out hereinafter.

In the drawings in which identical reference numbers refer to similar parts,

,Figure 1 is a longitudinal view, partly in section, showing the positions which some of the parts of the tool occupy when thedrive-shaft is in the top dead center position,

Figure 2 i822, view'similar to Figure 1 showing the positions of the parts 90 .after top dead center,

Figure 3 is;a similar view showing the posi* tions; of the'parts at the moment the'percussive element strikes the working implement and Figure 4 is a similar view showing the positions of the tool parts 90 before top dead center position of the drive shaft.

Referring now to the drawings for a-detaile'd description 'of the invention and, at first, more particularly to Figure 1, the tool,-shown-as a preferred form of the invention, comprisinga driving element, whichmay be any suitable motor (not shown) having a rotating drive shaft, 9. percussive element for striking a working implement a series of blows, andsuitable means forconverting the rotary motion of the drive shaft into reciprocable movement of the percussiveelement.

The tool'casing it, comprises a cylinder barrel II and a motor housing |2 joined together by bolts l3 and nuts M at the flanges |5--|fi. At its forward end I! the cylinder barrel H is adapted to receive a working implement I8 and to this end a recess [9 is provided in the cylinder barrel having a bushing inserted therein. The recess |9 communicates witha chamber or cylinder2 formed within the cylinder barrel I through an aperture 22 in the casing wall 23 between the recess I9 and the cylinder -2|.

A working implement it is inserted into .the bore 24 of the bushing 20 and has a collar 25 to abutthe outervend surface 26 of the bushing. The length of the working implement 18 from ,2 the :collar 25 to its inner end "21 is such tl'ft when the collar abuts the bushing the end of the working implement projects through "the aperture 22 and a sufficient "distance intothe'c'ylinder 2| "to'enable a piston 28 reciprocating within the cylinder to strike the endZ'l.

Any suitable means may be -employed to "convert' the rotary movement of the driving element to'reciprocabl'e movement of the percussive ele-- ment. In the form preferred by the applicant, the motor housing I2 is provided with a cylindrical opening 29 which forms "a continuation of the :cylinder 2| and "opensinto a chamber 30 housing the'rotating drive shaft 3| of the motor. The drive shaft 3| has a circular plate 3 2.having a crank-pin 33 thereon arranged eccentrically with respect to the shaft 3|.

A connecting rod 34 is connected to the crankpinat one end bybolts'35 and nuts 36 and has a free running fit on the crank-pin. At its opposite end 31 the connecting rod is joined, by a wrist pin '38, to a crosshea'd 3Q 's'li'dable "on the inner surface of the cylinder 2|. The motion'of the connecting rod 34 causes the 'crosshead39 'to reciprocate in the "cylinder 2| and the air displac'edas the crosshead reciprocates within the cylinder p'assesfrom one side to the other of the crosshead'through ports 40 inthe crossh'ead 39.

Reciprocable motion isimparted to the piston 28 bythe crosshead 39 through a resilient con nectiondesi'gned to allow the piston to'have some independent (forward movement with respect to the crosshead and provided with means for causin'g'theipiston to have such'independent forward movement at the moment of impact with :the working implement. In the form of the invention illustrated a spring assembly 62 is mounted on the crosshead'39 and a recess55 is provided in the piston 28 to receive the assembly. The recess has a depth, greater than the extended length of the spring 44 and this provides a certain amount of clearance at the ends of the spring enabling the piston to have free independent movement with respect to the spring assembly '62 and the crosshead 39. Such independent movement is I caused by the energy stored in the compression of thespringwhich imparts a velocity to the piston that carries it forwardly out of engagement with the spring to strike the Working implement. Thus'at the moment of impact the piston is completely free to move independently of the spring and crosshead.

More specifically, the resilient connection-com coil spring 44 mounted on the smaller section 43 thereof. One end 41 of the sprin 44 is confined by a circular disc 45 slidably mounted on the smaller section. Endwise movement of the disc 45 is limited by a shoulder 48 on the shaft 41 formed by the change in diameter.

The retainer-46 for the opposite end 49 .of the spring 44 is a cup-shaped member having a flange 50 at its open end for engagement with the spring. An aperture 6! is provided in the bottom of the cup portion of the retainer which allows the retainer to be slidably mounted onthe smaller section 43 of the shaft 41. The retainer 46 is held on the section 43 by means of a nut 54 and washer 53 threaded onto a stud provided in the end of the projection 4|, the diameter of the washer being greater than that of the aperture so that the washer 54 limits the endwise movement of the retainer. In the limited position of the retainer the end 49 of the spring 44 and the flange of the retainer extend beyond the end of the shaft 4| enabling the spring to be compressed considerably from that end'before the stud in the end of the shaft limits the compression.

A recess 55 is provided in the piston 28 to receive the resilient connection and has a depth greaterthan the over-all length of the spring assembly 62. The recess 55 has a bore 56 slightly larger than the diameter of the spring and accommodates the entire spring assembly 62 within its confines. A metal snap ring 57 is inserted in a groove 58 at the mouth 59 of the recess 55 and when in place prevents the spring assembly from withdrawing from the recess in the piston. Longitudinally disposed grooves 60 in the periphery of the piston 28 allow theair in the cylinder 2| to transfer from one side of the piston to the other as the piston travels in the cylinder.

It will be noted that the spring may be compressed from either end and that such compression of the spring 44 is caused by the piston moving relatively to the crosshead. If the piston moves away from the crosshead the snap,

ring 51 engages the retainer 45 and compresses the spring from the upper end 47. If the piston moves toward the crosshead the bottomv of the recess 5.5 in the piston engages the retainer 46 and compresses the spring from the lower end 49. However, the clearance providedbetween the recess and the spring assembly allows the pis-v ton to have some reciprocable movement independently of the crosshead and the spring assembly.

In the normal operation of the tool, the rotation of the drive shaft is converted to reciprocation of the crosshead as hereinbefore described. After the normal operating speed of the motor is reached the cycle of operation becomes stabilized and proceeds in a manner described below.

Referring now to Figure 4' the crosshead 39 is shown at a position 90 before the top dead center position and is at the mid point of its stroke travelling upwardly at its greatest velocity. The inertia of the mass of the piston 28 causes its movement to lag behind that of the crosshead and as a result the crosshead moves away from the piston until the snap ring 51 engages the oil";- cular disc 45. In the acceleration of the piston the spring 44 is compressed by the snap ring 51 and energy is stored therein. At the instant shown in Figure; the piston 28 is travelling upwardly with increasing velocity.

In Figure 1 the crosshead has reached the top dead center position. The piston 28, however, because of its inertia and because of the velocity imparted to it by the energy stored in the compression of the spring 44, continues in an upward direction, relieving the compression of the spring from the upper end 47, and compresses the spring 44 from the lower end 49, again storing energy therein.

The piston continues upwardly while the crosshead starts its downward travel and the spring continues to be compressed from the lower end. At a point between the top dead center position and after top dead center the inertia of the piston is overcome and the pistons upward travel is halted. A maximum compression of the spring has occurred and the energy stored therein now begins to accelerate the piston downwardly.

Figure 2 shows the crosshead at the mid point of its downward stroke travelling at its greatest velocity. V The piston 28, at this point, is travelling downwardly with increasing velocity. However, the velocity of the piston is not great enough at this time to allow the piston to move away from the crosshead to a point which would enable the spring to assume its unstressed position, consequently, the spring 44 is still compressed from its lower end 49.

In travelling from the position shown in Figure 2 to the bottom-dead center position shown in Figure 3 the velocity'of the crosshead decreases until the downward travel of the crosshead is halted. At the same time, the energy stored in the compression of the spring 44 increases the velocity of the piston 28 to a point where it exceeds the velocity of the crosshead. As a result there is relative movement of the piston away from the crosshead 39 until the piston reaches a point which allows the spring 44 to extend to its normal length. The energy stored in the compression of the spring has imparted a high velocity to the piston which now causes it to move independently of the crosshead and the spring and out of engagement therewith to strike against the working implement. Figure 3 shows the positions of the parts at the moment of impact between the piston and the working implement. I p p The weight of the piston, the stiffness of the spring and the frequency-ofthe drive shaft revolutions are carefully selected so that the piston rwill disengage from the spring assembly just prior to the moment of impact with the working implement. As mentioned above, the depth of the re-' cess 55 in the piston 28 is greater than the extended length of the spring 44. When the crosshead is at bottom dead center position the piston has reached a point which allows the spring 44 to be completely extended and is no longer in contact with the spring 44. The velocity of the piston causes it to continue downwardly and to strike the working implement a sharp blow while still disengaged from the spring 44. As a result the shock of impact is not transmitted to the spring 44 and consequently it has a much longer life.

After striking the working implement I 8 the piston rebounds compressing the spring from its lower end. The velocity of the crosshead is now increasing and very quickly exceeds that of the rebounding piston. Inertia of the piston causes its movement to lag behind that of the crosshead, consequently, the spring 44 soon is fully extended and then compressed from its upper end by the piston as shown in Figure 4 whereupon the cycle of operation described above is repeated.

macea The length of the recess needno't be greater thanthe length of ,the spring, Itis possbile to employ many constructions having, a recess of shorter length than thespring without departing from the spirit of the applicant's invention and it is to be understood that the foregoing description is merely illustrative of the preferred form of the applicants invention and that the scope of the invention should not be limited thereto,- but should be determined by the scope of the appended claims. I

I claim:

1. A percussive tool comprising a casing having a chamber, a reciprocable member in the chamber, a working implement in the casing, a reciprocable piston in the chamber for striking the working implement actuated by said member and capable of independent forward movement with respect thereto, a resilient member for causing the piston to so move forwardly tostrike the working implement, and a retainer for disengaging the resilient member from the piston before the piston strikes the working implement.

2. A percussive too1 comprising a casing having a chamber therein, a rotary drive shaft in the chamber, a working implement, a reciprocable member in the chamber, means for converting the rotary motion of the drive shaft to reciprocable motion of the member, a reciprocable piston in the chamber for striking the working implement actuated by said member and capable of independent forward movement with respect thereto, a resilient member in the chamber for causing the piston to so move forwardly with respect to the member to strike the working implement, and a retainer cooperating with the resilient-member to disengage the resilient member from the piston before the piston strikes the working implement.

3. A percussive tool comprising a casing having a chamber therein, a rotary drive shaft in the chamber, a working implement, a reciprocable member in the chamber, means for converting the rotary motion of the drive shaft to reciprocable motion of the member, a reciprocable piston in the chamber for striking the working implement actuated by said member and capable of independent forward movement with respect thereto, and a spring interposed between the reciprocable member and the piston for causing the piston to so move forwardly with respect to said member and to strike the working implement, and a retainer for disengaging the spring from the piston before the piston strikes the workin implement.

4. A percussive tool comprising a casing having a chamber therein, a rotary drive shaft in the chamber, a working implement, a reciprocable member in the chamber, means for converting the rotary motion of the drive shaft to reciprocable motion of the member, a reciprocable piston in the chamber for striking the working implement actuated by said member and capable of independent forward movement with respect thereto, a spring in the chamber for causing the piston to so move forwardly with respect to said member, and means for preventing engagement of a retainer for the spring to prevent the spring with the .piston at the moment the piston strikes the working implement.

5. A percussive tool comprising a casin having a chamber therein, a rotary drive shaft in the chamber, a working implement, a reciprocable member in the chamber, means for converting the rotary motion of the drive shaft to reciprocable motion of the member, a reciprocable piston in the chamber for striking the working imple- 6. men-t connected to said member' and capable of. independent forward movementwwithv respect thereto, a-spring on the reciprocablemember'for causing the piston to so move forwardly witnrespect to the member and to strike the" working implement, and a retainer cooperating with the spring to disengage the spring from the piston before-the piston strikes the working implement.

6. A percussive tool comprising a casing havinga chamber therein, a rotary drive shaft-in the chamber, a reciprocable member in the chamber, means for converting the rotary'm'otion-of' the drive shaft to reciprocable motion of the memher, a workingim'p'len'ientin the casing} a reciprocable piston in the chamber for "-striking the workingimplement, aspring mounted on the reciprocable member for causin the piston to strike the working implement, a recess in the piston to receive the spring, said recess having a length greater than the extended length of the spring to allow the piston to have some independent reciprocable movement with respect to the spring and a retainer for the spring to disengage the spring from the piston before the the piston strikes the working implement.

7. A percussive tool comprising a casing having a chamber therein, a rotary drive shaft in the chamber, a reciprocable member in the chamber, means for converting the rotary motion of the drive shaft to reciprocable motion of the member, a working implement in the casing, a reciprocable piston for striking the working implement capable of relative movement with respect to the reciprocable member, and a spring interposed between the reciprocable member and the piston adapted to be compressed from either end by the piston moving relatively to the reciprocable member and acting to cause the piston to strike'the working implement.

8. A percussive too1 comprising a casing having a chamber therein, a rotary drive shaft in the chamber, means for converting the rotary motion of the drive shaft to reciprocable motion of the member, a working implement in the casing, a reciprocable piston in the chamber for striking the working implement, a spring interposed between the reciprocable member and the piston for causing the piston to strike the working implement, and surfaces on the piston for compressing the spring from one end thereof when the piston moves toward the reciprocable member and for compressing the spring from the other end of said spring when the piston moves away from the reciprocable member, said surfaces being spaced at a distance greater than the length of the spring.

9. A percussive too1 comprising a casing having a chamber therein, a rotary drive shaft in the chamber, a crosshead in the chamber, a connecting rod connecting the crosshead to the drive shaft for converting the rotary motion of the shaft to reciprocable motion of the orosshead, a working implement in the casing, a reciprocable piston in the chamber for striking the working implement, a spring for causing the piston to strike the working implement mounted on the orosshead, and surfaces on the piston to compress the spring from either end, said surfaces being spaced at a distance greater than the extended length of the spring.

10. A percussive tool comprising a casing having a chamber therein, a rotary drive shaft in the chamber, a crosshead in the chamber, a connecting rod joining the crosshead to the drive shaft for converting the rotary motion of the shaft to reciprocable motion of the crosshead. a working implement in the casing, a reciprocable piston in the chamber for striking the working implement, a. projection on the crosshead, a spring interposed between the crosshead and the piston for causing the piston to strike the working implement, a pair of retainers for the spring slidably mounted on the projection, said retainers being slidable inwardly toward one another for compressing the spring, a recess in the piston to receive the spring, said recess having a length greater than the distance from one retainer to the other, and a ring removably mounted in the mouth of the recess to confine the spring therein.

HAROLD C. REYNOLDS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 709,820 Jackson Sept. 23, 1902 1,841,781 Bisschop et al Jan. 19, 1932 1,959,516 Baker May 22, 1934 10 2,013,296 Baker Sept. 3, 1935 2,260,172 Decker Oct. 21, 1941 

